Garmin 935 Battery

My 935 is 4 years old (yours too, because the 935 was introduced in 2017).

With gps activities my battery lasts about 10 hours. This used to be 20+ hours. 
This is either a bug in garmin software (not at all unlikely, given garmin software is full of bugs) or batterydegeneration.

When my watch was new I had to charge it about every other week, now it lasts less than a week. Say I charged it every week for the last 4 years, that means 200 charge cycles. Thatks really nothing. Normal batteries will keep 80% of their capacity for 500 cycles. Good batteries for 1000 cycles.

So, either it’s a bug in the fiirmware (which is unlikely for garmin to fix) or garmin uses very lousy batteries. Both ways, nothing is going to change for the better, I’m afraid. 

My forerunner 935 is my first garmin device. So far I’ve learned that Garmin has many features, quite a lot don’t work very well or are not that useful.  Garmin support in the Netherlands is very bad. Garmin software is even worse. And Garmin is a company driven by marketing.

aaronc_smith said:

Is this normal degradation in battery life?

A li-ion battery should survive about 500 charge cycles without a significant decrease in performance, perhaps more than that in some circumstances. I'd say this kind of degradation is not normal, but on the other hand such things do happen. Li-ion battery failures are not uncommon. I'd start with simply rebooting the watch, because sometimes a software glitch can cause increased battery drain.

thanks for the replies. I expected is to degrade over time, just didn't quite think it would be this much after 4 years (yes, 4, not 5).

Lost about 10% charge overnight last night while sleeping. Luckily I'm still in injury mode and not really training at all this year (don't expect to do much this summer) so just recharging regularly is fine, but I was hoping for a bit more life out of this battery than I got.  

i bought mine in April 2017 and i'm grateful that it's battery life is not severely diminished. i do about 2-3 hrs of GPS activity a week on average (sometimes a lot more, but sometimes less) and i would say overall capacity is maybe down 5-10% from the first day which is to be expected. (i can project about 21-22 hrs of GPS activity vs 24 when new).

i wonder what firmware you guys are running. after seeing many different firmware updates cause glitches on my watch, i found stability with FW13.30 and haven't upgraded it since. that means that some of my watch faces can't be updated, but i'm content with how the watch functions and would be scared to upgrade, especially after many reports of people experiencing bad battery life in subsequent FW updates after 13.30.

have any of you considered rolling back the firmware (i seem to recall -- maybe incorrectly -- that it was possible although a fair bit of work)?

interesting.  Mine has been autoupdating and says I'm on 20? (I've never paid attention to it).  

It looks like I'm losing a little under 1% of charge per hour of just normal wear, without any activities. 

yes. your watch will auto update unless you manually disable it from doing so. all of these messages about short battery life kept me from moving beyond 13.30. i see about 6-7% usage with a 3rd party face that updates seconds and HR at 1hz without GPS usage. so it's a 2 week watch if i'm not doing GPS activities.  taht being said, i charge every 7-10 days ... trying to avoid dipping below 20% which i know is hard on lithium-ion batteries.

again, i have no clue if it's possible to downgrade, but it's certainly something i would try if i had excessive battery burn like you. 

has this battery consumption slowly ramped up or do you recall a point in time where it abruptly went up?

last few months has gotten significantly work, but last few weeks accelerated. 

sorry to hear. i think the FW21 update happened a couple of months ago according the forum sticky... i'd search around and see if a fW rollback helps...or at the very least, try a soft, semi-hard, and then hard reset to see if that helps things.

I'll look into it.  thanks for your help. 

No a new strange thing... I just did a short :20 no-GPS workout. Battery started at 47%, when I was finished it said 4%... but then it started climbing and :30 later the battery is up to 20%.  

Definitely seems like a firmware issue.